Actually, NHS staff have been at no greater risk than the wider community. I initially felt as you do i.e. that they were walking into a war zone where their lives were at risk when entering their place of work.
But there are around 1.5 million people working for the NHS, and the number that have died is the same rate as exposure as the general population.
It seems that bus drivers have been disproportionately affected, though, as have security guards (e.g. at shop entrances etc.).
The idea that being in a hospital is very dangerous has itself caused great damage with people failing to turn up with suspected cancer and heart attack (etc.) conditions.